It was considered one of the bigger paradoxes for years. Back in 2003, Warren Buffett famously dubbed derivatives “financial weapons of mass destruction” and yet over the next several years went ahead and entered a number of the contracts, including both equities and credit, ostensibly by selling CDS to collect up monthly premiums. However, at least when it comes to CDS, after several years of Berkshire trimming its credit derivative exposure, it is now completely out. Meanwhile, Citi is loading up on any CDS it can find…